India, Nov. 22 -- The brief respite - and that too only in relative terms - that Delhi experienced from "severe" air quality faded away by Friday evening as the Capital's air deteriorated again, returning to the worst classification of pollution.

On Friday, in fact, saw Delhi saw a steady deterioration in pollution levels, with the Air Quality Index (AQI) plummeting from 374 ("very poor") at 9am, to 376 at 11am, then 397 at 5pm, 401 ("severe") at 6pm, and worsening to 414 by 10pm, according to data furnished by the Central Pollution Control Board's (CPCB).

The day's official reading, taken at 4pm, was 393 ("very poor").

According to CPCB data, out of the 39 AQI stations across the city active on Friday, only six stations were in "sever...